What Size Fuse For 4 Gauge Wire

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Wire Gauge (AWG) Estimator

Choosing the right wire size is essential for SAFETY (fire hazard due to max current chapters) and PERFORMANCE (intermittent problems due to voltage drop) of your electric organisation.
Wire gauge depends on CURRENT and LENGTH of the wire. This means even if your friend installed the same components (e.g. inverter, refrigerator, etc.) as you, you most likely demand dissimilar wire gauge.
Wire sizing per ABYC standards for 12V DC, 105°C copper wire conductor. This figurer does non supersede manufacturer recommendations and is for reference only; have your diagram and installation checked by a professional.

How can we help today?

I KNOW THE LOAD CURRENT Preferred. Meliorate accuracy.

I DON'T KNOW THE LOAD Electric current, BUT I KNOW THE FUSE SIZE Easier, but may result in slightly oversized wire (which is totally fine in terms of condom and performance; the downside is the cost!)

Load Electric current Maximum electric current flow expected from the load.

Fuse size As recommended by the manufacturer.

(amps)

Wire Length Circular-trip (positive + negative).

(pos+neg, feet)

Voltage Drop The loss of free energy equally current moves through a wire results in voltage drop. A larger wire offers less resistance and therefore minimize voltage drop. We recommend 3%.

(%)

Fuse/Billow If yous don't know, we will use:
LOAD CURRENT X 1.4

(amps)

I don't know, tell me!
Per owner's manual.

Derating Factors Factors that impact the ampacity or the voltage drib of wires

Wire in ambient temperature of 50°C (122F) or more? This option is equivalent to "In Engine Room" per ABYC standards, which REDUCES THE WIRE AMPACITY BY 15%. This is most probable the case for wire running in ceiling or wall, every bit it gets much hotter than in the living space of the van (especially for dark color van).The max current that the wire can safely carry is reduced considering it has less capacity to dissipate the rut generated by the current menstruum.
Load runs continuously for twenty minutes or more? This option increases the load electric current by 25% for voltage drop calculation (but not for the fuse/breaker calculation). This is to mitigate the fact that more rut builds upward in the wire if the current flows continuously.
Wire in conduit, insulation or arranged with 2 (or more than) wires? Wire ampacity is reduced by xxx%, since its ability to dissipate heat generated past current flow is reduced.

Recommended Wire

AWG ?

AMPACITY: ?A Maximum current that a wire tin can carry continuously without exceeding its temperature rating.

DERATED AMPACITY: ?A Corrected ampacity when taking derating cistron(due south) into business relationship.

Fuse likewise small

ENTER FUSE

OUT OF RANGE

AWG ? DUPLEX

AWG ? BLACK

AWG ? Crimson

*You tin select the wire length on Amazon

How this wire calculator works

Based on Load Current:

Using load_current and length, we first find the wire judge that meets the selectedvoltage_drop.
We find a wire gauge for which the ampacity is higher than the fuse size (fuse size per owner's manual, otherwise we compute it every bit follows: fuse_size = load_current x 1.4).
Nosotros compare 1. and 2. above and proceed the wire with the largest gauge.
Voilà!

Based on fuse size:

We presume that: load_current = fuse_size/i.25 (information technology is generally accepted that a fuse must be at minimum 125% the size of the load current)
Using load_current and length, we compute the wire estimate that meets the chosen voltage driblet.
We detect a wire gauge for which the ampacity is higher than the fuse size.
We compare 2. and 3. above and keep the wire with the largest gauge.

Derating Factors:

Wires can carry a certain amount of current continuously and no more; more electric current ways the wire volition overheat (and cook) as it cannot dissipate the heat that is generated by also much current period. That characteristic is called AMPACITY (maximum current that a wire can carry continuously without exceeding its temperature rating). Certain factors reduce the ampacity rating of wires and the voltage drop likewise:

Ambient temperature of fifty°C (122F) or more

A wire located in ambient temperature of 50°C (122F) or more than loses its power to dissipate heat, and, therefore, its ampacity is reduced by 15%. (notation: this is per ABYC standards "In Engine Room"). This is most probable the case for a wire running in the wall/ceiling of a van considering temperature in there is much higher than in the living space (that'due south especially true for darker colour vans).

Load runs continuously for 20 minutes or more

A wire that carries a electric current menstruation for a long duration (~20 minutes) builds up more rut. As the temperature of a wire increases, so does the resistance to current flow = more voltage drop. To mitigate this factor, the load electric current is increased past 25% for the voltage drop adding (only non for the fuse/breaker size calculation). This is not an ABYC requirement at the moment; even so, it is generally accepted by marine product manufacturers (such as Blueish Sea).

Wire in conduit, insulation, or bundled with ii (or more) wires

A wire located in a conduit, sheath, running through insulation, or bundled with ii (or more) wires loses its ability to dissipate heat, and therefore, its ampacity is reduced past 30%. This is non an ABYC requirement at the moment; nevertheless, it is generally accepted by marine product manufacturers (such as Blue Ocean).

Making things piece of cake

Did we mention you really don't demand to use this computer? :P Our wiring diagram features customizable components (solar, alternator, shore, inverter, 12V loads), a built-in wire estimate (AWG) calculator, and it will output the wire lengths & terminals y'all demand to buy. It doesn't get easier than this! Here information technology is in action:

Maxxfan Wire Sizing Example

Method i: Calculate Wire Gauge from Load Current (preferred)

Meliorate accuracy

Load Electric current

Always apply the maximum electric current that the load is expected to describe. The Maxxfan can draw up to 2.8A at the highest speed in steady state (according to our Simarine Pico Monitor). However, any load with a motor draws more than current during startup for a very brusque catamenia of time, so we'll go alee and add about fifty% buffer to account for startup. If you have no inkling what current to use as an input, information technology's OK to use the FUSE SIZE that the manufacturer recommends. As a issue, you'll get slightly oversized wires (which is quite good for condom, performance, and durability).

Wire Length

The wire length input is always the round-trip length. The round-trip length is the sum of the positive and the negative wires. Remember that a duplex wire packs the positive and the negative into a single wire, so the round-trip length is equal to twice the duplex length.

Voltage Drib

There is a loss of energy (voltage drop) as current moves through passive elements (terminal, fuse, wire, etc.); a smaller wire means more voltage drib. For example, if we size the wire for 3% voltage driblet (bigger wire), the voltage will go from 12V at the fuse cake down to 11.64V at the Maxxfan. If nosotros size it for 10% voltage drop (smaller wire), the voltage at the Maxxfan will exist 10.8V; this can become a problem equally the bombardment voltage goes down (low SOC). For best operation, we recommend iii% (5% would exist OK as well).

FUSE/Breaker

Overcurrent protection devices (fuse/breaker) protect the wire (not the load) from beingness used over its ampacity; information technology's the weakest link! Therefore, a fuse/billow should exist smaller than the ampacity of the wire but big plenty so that it doesn't blow during normal operation of the load. The easiest way to determine the fuse size is to follow the manufacturer recommendations! And so check the possessor's transmission or specifications canvass. Can't find it? OK then. Equally a full general rule, the fuse size can exist determined as follows: LOAD Electric current 10 ane.4 and so round up to the next available fuse. In the Maxxfan scenario: 4A x 1.4 = 5.6A = vii.5A fuse. All the same, information technology looks like the manufacturer recommends a 10A, fuse then we'll stick to that.

Wire in ambient temperature of 50°C (122F) or more? --> Yep, considering the wire is routed in the ceiling!
Load runs continuously for 20 minutes or more? --> Oh yeah, definitely!
Wire in conduit, insulation, or arranged with 2 (or more) wires? --> Not in our case.

Method 2: Calculate Wire Approximate from fuse size

Easier, but may result in slightly oversized wires (which is totally fine in terms of safety and performance; the downside is the cost!)

Fuse Size

In the scenario where we have no inkling how much electric current the Maxxfan draws (load electric current), we'll use the fuse size instead. Using our Google super skills, we find that the manufacturer recommends a 10A fuse:

Wire Length

Voltage Drop

When basing our calculation from the fuse size, we similar to use 5% voltage drop (instead of iii%). This is to "compensate" for the slightly oversized wire that this method gives.

Wire in ambient temperature of 50°C (122F) or more than? --> Yep, considering the wire is routed in the ceiling!
Load runs continuously for xx minutes or more? --> Oh yeah, definitely!
Wire in conduit, insulation, or bundled with ii (or more) wires? --> Not in our case.

1500W Inverter Wire Sizing Example

Electric current

Equally always, we want to use the maximum electric current as an input. 1500W/12V = 125A is an oversimplification. Actually, the inverter can work downwardly to 10.7V and the efficiency ratio is around 85%, then: 1500W/x.7V/0.85 = 165A. But according to the specifications sheet, the "maximum input current" is 200A. We always follow the manufacturer recommendations, and so:

Length

As always, we want to use the round-trip length as an input. That's the sum of the positive and negative wires:

Voltage Drop

Reputable inverter brands are quite aggressive with voltage drop; we've seen it in the 2% range. Why? Because they intendance about how their production performs in the real-world, not but on the specifications sail. For example, nigh inverters stop working beneath 10.7V; if the inverter was wired for 10% voltage drop, information technology means it won't piece of work when the bombardment accuse (SOC) is at around 60%-70% (for AGM), which tin happen very frequently in the real world...

Fuse/Breaker

According to the Samlex owner's transmission, a fuse of 200A is recommended:

Wire in ambient temperature of 50°C (122F) or more? --> Yes, fifty-fifty if that might not be the case often.
Load runs continuously for 20 minutes or more than? --> Unlikely, merely we can't say it'due south never going to happen.
Wire in conduit, insulation, or bundled with 2 (or more than) wires? --> Non in our case.

The inverter is the most finicky and unsafe function of an electrical organization. While you tin utilize this computer for sizing the wires, we highly recommend to follow the manufacturer recommendations from the owner's manual (fuse size, wire approximate, and wire length). That'll ensure the inverter installation is safe and performs as it should. (Expect to find different recommendations between this calculator and different inverter brands; no i seems to utilise the same calculation/factors...)

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About-Us-Narrow

Hello! Nosotros're Isabelle and Antoine 🙂 In 2017, nosotros sold our firm (and everything in it), quit our engineering careers, and moved into our self-built campervan. We've been on the road since and so, and every day is an opportunity for a new adventure; nosotros're chasing our dreams, and hopefully information technology inspires others to do the aforementioned!